type_traits.hpp

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#if !defined(TYPE_TRAITS_FF88A4C7_86DE_434F_93B7_B03DCA5B4578_H)
#  define TYPE_TRAITS_FF88A4C7_86DE_434F_93B7_B03DCA5B4578_H


#  include <type_traits>

namespace pgs { 

  //-- Borrow from the future

  //C++14
  template <class T>
  using decay_t = typename std::decay<T>::type;

  //C++14
  template <bool B, class T = void>
  using enable_if_t = typename std::enable_if<B, T>::type;

 // C++17
  template <class B>
  struct negation : std::integral_constant <bool, !B::value>
  {};

  //--
  
  template <class T, class U>
  using not_is_same = negation<std::is_same<T, U>>;

  namespace detail {
    struct no {};
  }//namespace detail


  template<typename F, typename...Args>
  struct is_callable {

    template<class G, class...Qs>
    static auto check(G g, Qs...qs) -> decltype(g(qs...));

    static detail::no check(...);

    static constexpr bool value = 
     !std::is_same<
        detail::no
      , decltype(check (std::declval<F>(), std::declval<Args>()...))>::value;


  };

}//namespace pgs

#endif